The FBI opened an investigation Monday into possible civil rights violations arising from the death of 18-year-old Michael Brown, said Cheryl Mimura, a spokeswoman for the FBI’s St. Louis field office. Police say Brown was shot multiple times Saturday in a scuffle with an officer in Ferguson, a predominantly black suburb. Mimura said the FBI is monitoring the case and working with St. Louis County police.

The killing drew criticism from some civil rights leaders, who referred to the 2012 racially charged shooting of 17-year-old Trayvon Martin, an unarmed African-American, by a Florida neighbourhood watch organizer who was acquitted of murder charges. Civil rights leader Rev. Al Sharpton called the shooting “very disturbing” and said he planned to go to Ferguson to meet with the family.

A candlelight vigil for Brown was held Sunday, and tensions erupted later that night. Nearly three dozen people were arrested after a crowd looted and burned stores, vandalized vehicles and taunted officers.

Mimura noted that the FBI would be investigating such a shooting regardless of the public attention.

Tensions erupted in Ferguson after a candlelight vigil Sunday night. Crowds looted and burned stores, vandalized vehicles and taunted officers who tried to block access to parts of the city. Nearly three dozen people were arrested, though the area was relatively quiet early Monday. Witnesses said the vandals were likely opportunistic outsiders who arrived looking for a chance to steal.

WATCH: Many stores were looted during the protests including a Quiktrip gas station and a sporting goods store, both incidents were caught on camera

“The small group of people are creating a huge mess,” Mayor James Knowles said. “Contributing to the unrest that is going on is not going to help. … We’re only hurting ourselves, only hurting our community, hurting our neighbours.”

Ferguson’s streets were relatively quiet early Monday. Some debris littered the area but crowds had dispersed.

32 people were arrested for various infractions including assault, burglary and theft, authorities said. St. Louis County police spokesman Brian Schellman said two officers suffered minor injuries and that there were no reports of civilians hurt.

WATCH: Angry protests and looting in Ferguson, Missouri on Sunday night after a vigil for a black teen who had shot and killed by police.

Several businesses were looted, including a check-cashing store, a boutique and a small grocery store. People took items from a sporting goods store and a cellphone retailer, and carted rims away from a tire store. Some climbed atop police cars as the officers with riot shields and batons stood stoic nearby, trying to restrict access to the most seriously affected areas.

St. Louis County Executive Charlie Dooley said there were no reports of injuries as of about 11 p.m. But there were scattered reports of assaults into the very early morning. Authorities said tear gas had been used, but would not immediately confirm media reports of gunfire.

County Police Chief Jon Belmar said that on Saturday, an officer encountered Brown and another man outside an apartment complex in Ferguson. One of the men pushed the officer into his squad car and they struggled. Belmar said at least one shot was fired from the officer’s gun inside the police car. Ferguson Police Chief Tom Jackson said authorities were still sorting out what happened inside the police car. It was not clear if Brown was the man who fought with the officer.

The struggle spilled out into the street, where Brown was shot multiple times. Belmar said the exact number of shots wasn’t known and that all shell casings at the scene matched the officer’s gun. Police were investigating why the officer shot Brown, who police have confirmed was unarmed.

Jackson said the second person has not been arrested or charged and it wasn’t clear if he was armed.

A man leaves a store on Sunday, Aug. 10, 2014, in Ferguson, Mo. A few thousand people crammed a suburban St. Louis street Sunday night at a vigil for unarmed 18-year-old Michael Brown shot and killed by a police officer, while afterward several car windows were smashed and stores were looted as people carried away armloads of goods as witnessed by an an Associated Press reporter.

AP Photo/St. Louis Post-Dispatch, David Carson

Ferguson Police Chief Tom Jackson told KSDK-TV there’s no video footage of the shooting from the apartment complex, or from any police cruiser dashboard cameras or body-worn cameras that the department recently bought but hasn’t yet put to use.

Jackson said blood samples were taken from Brown and the officer who shot him. Toxicology tests can take weeks to complete.

Earlier Sunday, a few hundred protesters gathered outside Ferguson Police headquarters. Some marched into an adjacent police building chanting “Don’t shoot me” while holding their hands in the air. Officers stood at the top of a staircase, but didn’t use force; the crowd eventually left.

A large crowd gathers at the candlelight vigil, Sunday evening, Aug. 10, 2014, in Ferguson, Mo.

AP Photo/St. Louis Post-Dispatch, J.B. Forbes

Brown’s mother, Lesley McSpadden, said she didn’t understand why police didn’t subdue her high school graduate son with a club or stun gun, and that the officer involved should be fired and prosecuted.

The killing drew criticism from some civil rights leaders, who referred to the 2012 racially charged shooting of 17-year-old Trayvon Martin by a Florida neighbourhood watch organizer who was acquitted of murder charges.

“We’re outraged because yet again a young African-American man has been killed by law enforcement,” said John Gaskin, who serves on both the St. Louis County and national boards of directors for the NAACP, the oldest American civil rights group.